Merge pull request #4768 from pwojcikdev/observer-set-const-refs #2380

Job	Run time
Linux [UBSAN] [lmdb \| clang]	40m 41s
Linux [ASAN] [lmdb \| clang]	39m 46s
macOS [UBSAN] [lmdb \| clang]	36m 37s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	41m 16s
macOS [ASAN] [lmdb \| clang]	31m 30s
Linux [TSAN] [lmdb \| clang]	43m 11s
macOS [TSAN] [lmdb \| clang]	34m 22s
Linux [LEAK] [lmdb \| clang]	40m 46s
macOS [UBSAN] [rocksdb \| clang]	41m 10s
macOS [ASAN] [rocksdb \| clang]	38m 13s
Linux [UBSAN] [rocksdb \| clang]	52m 41s
macOS [TSAN] [rocksdb \| clang]	54m 4s
Linux [ASAN] [rocksdb \| clang]	56m 28s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	57m 53s
Linux [LEAK] [rocksdb \| clang]	57m 53s
	11h 6m 31s

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